1. Field of the Invention
The present invention relates generally to a method of measuring the thickness of a thin film layer using an infrared thermal imaging system and, more particularly, to a method of measuring the thickness of a thin film layer using infrared radiation spontaneously emitted from a target surface instead of using reflected light, which two-dimensionally measures the thickness of the thin film of a coating layer using an infrared thermal imaging system.
2. Description of the Related Art
Coating is frequently used to protect a surface or to strengthen the function of the surface. The thickness of a coating trends toward a decrease so as to increase the economical efficiency of the coating. As the thickness of the coating becomes thinner, it is important to make the thickness of the coating uniform. For this purpose, it is required to measure the thickness of the coating.
For a conventional method of measuring the thickness of a thin film layer, point measurement using supersonic waves or an optical method has been mainly used. However, a method of measuring the distribution of the thickness of a thin film on a coated surface using the point measurement is problematic in that the method is just a sample test on the coated surface, and it is difficult to use the method of quickly detecting the distribution of the thickness because it takes a long time to measure the thickness. To solve the above-described problems, an optical measuring method has started to be used as a method of obtaining two-dimensional (2-D) thickness distribution at one time even though its accuracy is deteriorated compared to the point measurement. The conventional 2-D thin film thickness measuring method is designed to measure the thickness of a thin film in such a way that a measurement instrument emits a radiant ray (light) and measures reflected light, and the thickness of the thin film is measured using the deviation of reflexibility on a coated surface. However, the method is problematic in that a narrow-band filter is required because the method is weak with light reflected from the surroundings, a light source is required to emit the radiant ray, and the reflected light is required to be normalized with respect to the intensity of the emitted light because the distribution of the light emitted to a target surface is not uniform. Furthermore, the method is problematic in that the intensity of the reflected light considerably varies with the angle of the target surface.